Electromagnet



C. E. AVERY.

ELECTROMAGNET.

APPLICATION FILED MAR.27,19I7.

2 SHEETSSHEET 1.

C. E. AVERY.

ELECTROMAGNET. AFPLICATION FILED MAR. 27, 1917.

1,338,548. Patented Apr. 27,1920.

2 SHEETS-SHEET 2.

UNITED STATES PATENT crease;

CHARLES E. AVERY, OF TRENTON, NEW JERSEY, ASSIG-NOR T0 MANHATTANELECTRICAL SUPPLY COMPANY, INC, 013 JERSEY CITY, NEW JERSEY, A COR-PORATION OF MASSACHUSETTS.

ELECTROMAGNET- Specification of Letters Patent.

Patented Apr. 27, 1920.

Application filed March 27, 1917. Serial No. 157,738.

To all whom it may concern:

Be itknown that I, GHARLEs E. AVERY, a citizen of the United States ofAmerica, and residing in Trenton, in the county .of Mercer and State ofNew Jersey, have invented a certain new and useful Improvement inElectromagnets, of which the following is,- a specification.

My invention rel tes to electromagnets and particularly to alternatingcurrent magnets, the object of'my invention being to so construct amagnet of thistype as to eliminate the chatter of the armature andassociated parts which is commonly incident to the operation of themagnet due to the vibrations icaused by the alternating current, and tosecure an increased range of movement for the armature whether operatedby direct or alternating current.

In the following drawings,

Figure 1 is a plan, with cover removed, of an electromagnet foroperating a fire gong and in which my invention is embodied in one form;

Fig. '2 is a section through the magnet coils showing the armature andsupporting that brackets;

Figs. 3, 4 and 5 are sections on the lines 3-3, 4-4:, and 5-5, Fig. 1respectively;

Fig. 6 is a diagrammatic elevation of a modified construction;

Fig. 7 is a broken elevation at right angles to Fig. 6; and

Fig. 8 is an elevation and Fig. 9 a broken plan of one of the coilspools.

One of the difliculties incident to the useof alternating current toenergize electromagnets is the rapid oscillation constantly imparted tothe armature during the maintenance of the field. When the armatureoperates a switch, this oscillation results in \a'poor contact at thepoint ofengagement between the switch members. When the armatureoperates a gong hammer, it causes the hammer head to tremble against thegong and produces a. muflied instead of a clear sound. Various ways havebeen here- 'tofore devised which meet this difliculty with'more or lesssuccess, but none in so simple and eflicient a manner, I believe, a's

for which I now ask the grant of suitable patent protection.

Briefly stated my invention consists -1n so arranging the armature withrelation to the magnetic field that .upon energization of the magnet,the armature passes through the area of greatest magnetic attraction toa point at which said attraction is practically counter-balanced by theeffort (gravity, counterweight or spring) of -the armature to return tonormal position.

In the construction here shown the magnet comprises a pair of coils 10and 11 supported within the casing 12 by brackets 13 and 14: ofnon-magnetic material, such as brass. These coils are here shown woundin multiple, the lead wires 15 and 16 being connected to terminal plates17 and 18' mounted on a block 19 of insulating material carried by theside wall of the casing 12-and to which the wire mains entering throughthe conduit 20 are connected.

The armature 21 is rigid'with the spindle 22 pivoted on the bracket 23,and the gong hammer-24 is fast on the spindle 22 gong 25 when thearmature is drawn down so that it is swunginto contact with the as aresult of the energization of the magnet are substantially equal at bothpoints. The

armature-is pierced so that when operated the pole 26 passes into thearmature and the pole 27 passes internally through it, the holes beingsomewhat larger than the poles which cannot come in contact with thearmature. Aspring 28 may be attached at one end to the armature at 29and at its other end 30 to the casing to counter-balance to a largeextent the weight of the gong lever 24 and thus render the action of thearmature more delicate. Less current is thus required to actuate thegong lever.

Upon the energization of the coils a magnetic fieldis created which isapproximately illustrated in Fig. 2. As indicated in the drawing, thearmature normally lies bev the area X of greatest magnetic eflort. The Ithrow of the armature, however, under the influence of the magneticfield, carries it not only into this area but through it to a point ofrest against the non-magnetic bracket 14, at which point the magneticattraction is substantially counterbalanced by the tendency ofthe lever24 to return to its position of rest by gravity. The armatureconsequently lies quietly in this position without the usual trembleresulting from the oscillation of the alternating current in the magnetcoils. It is emphasized that the bracket 14 is of brass, or othernon-magnetic material, and has no influence upon the armature 21,.aswould be the case were the bracket of iron or like material.

In fire alarm systems a weak supervising current is constantlymaintained on the signal circuit to insure the maintenance of the latterin operative condition. The position of the armature 21 must thereforebe such with relation to the magnetic field that it is not materiallyaffected by the slight pull of the field under the influence of thesupervising current. On the other hand, it must be sufliciently close tothe maximum effort df the 'field to respond at once and with certaintywhen the operating current is impressed upon the circuit. Moreover, itstendency to return to position of rest must be sufliciently strong toovercome the weak vmagnetic field caused by the supervising current sothat upon the break of the operating circuit the lever returns toposition, its

inertia being sufiicient to carry it through gongs, since the magnet maywith equal value be utilized to operate a contact lever or other member.It is applicable to all A. Cfima end of its stroke is desired.

"It will be noted that the armature ahd the magnet core are bothlaminated, the advantages of which construction are wellknown. It willalso be noted that as an incident to'the accomplishment of the resultstated, the branch 27 of the magnet core extends beyond the outer faceof the armature when the latter is operated by the magnet. Th1s has adetermining effect inlocating the magnetic field in the desired area. iThe nonmagnetic brackets 13 and 14 are s lit or slotted to avoidtheformation of eddy currents which if present would require greaterpower to energize the magnet, as is well understood by those skilled inthe art.

One detail of value in the construction of the-magnet is illustrated inFig. 8 and reets in which the elimination-of the vibration of theactuated memberitt he coils a sufiicient lates to the spool upon whichthe magnet coil is wound. The hollow body 31of the latter head 34. Bothheads areretaine in theirv extreme positions against the flanges 32 and35 by the coil'when the latter is wound on the spool. The projectingportion 36 of the spool body is engaged by the bracket 14 on Which oneend of the magnet is supported. In order to prevent the edges of thelaminations of the core from coming into contact with. the walls of th-spindle 31 insulating strips 37 may be intgrp'osed. One of ,thesestrips is preferablyjlocated on he same side of the spindle as't'hespaced edges a and b of the sheet, thus serving to maintain these edgesspaced apart and prevent the formation ofeddy currents in, the spindle.

In Figs. 6 'and 7 I have illustrated diagrammatically. a modifiedconstruction in which the armature 38 is mounted on an axis 39 Cparallelto the plane of thebranches '26 an 27 of the core instead of at rightangles,

thereto as in Figs. 1 to, 5. The magnetic field is the same in thisarrangement as in the one above described, and the location of thearmature with reference thereto may be similarly predetermined. Theadvantage of the construction in Figs. 1 to 5 is merely one of greaterleverage for the armature within a iven space.

arious modifications in details of construction will readily occur tothose skilled in the art which do not depart from what I claim as myinvention.

1 claim 1. An alternating current magnet comprising magnet coils, polepieces therefor projecting be 0nd the ends of the istance to establishan area of maximum magnetic attraction be yond the ends of the coils, arigid armature spaced from said poles but pivoted at a point such that,on excitation of the magnet, the armature is free to pass through saidarea of maximum attraction, together with igid stop means halting saidarmature in sta e position at a magnetic attraction is su stantiallycounterbalancedby the effort of the armature to return to normalposition.

2. In a construction such as specified in claim 1, a lever associatedwith said armapoint at which the ture and moved to ope ative position bythe latter on the excitation of the magnet.

3. In a construction such as specified in claim 2, a spring arm carriedby said lever and temporarily flexed into action by the .being movedinto operative position by the impingement of the armature against itsmovement of the "armature on the excitation stop. 4 o of the magnet.

4:- In a construction such as specified in In testimony whereof I havesigned my 5 claim 1, a lever rigid with said armature name to thisspecification.

and extending on the opposite side of the pivotal mounting of thearmature, said lever CHARLES E. AVERY.

